(1) Field of the Invention
The present invention relates to an injection method in which brine for curing, seasoning liquid or another liquid substance is injected to a block of pork, beef, poultry meat or another meat and the liquid substance is uniformly dispersed and a pickle injector for use in the method. Also, the present invention relates to a method of manufacturing meat products of pork, beef, poultry meat or the like, for example, cooked meat products or a raw ham or other uncooked meat products in a short time by using the injection method.
(2) Description of the Related Art
In meat processing there is a need for uniform dispersion of curing agent or seasoning in meat. In recent years, it is a mainstream to use a multi-needle pickle injector.
By a method in which the multi-needle pickle injector is used, products, in which additives included in brine for curing or seasoning liquid are dispersed more uniformly than former days, can be manufactured. However, immediately after injection, the liquid is accumulated in portions into which needles are stuck. Therefore, after a dynamic stimulus is given with a tumbling machine, a massage machine or the like, a green meat needs to be cured until the brine for curing or the seasoning liquid permeates through the green meat and is uniformly dispersed. Then, the process can advance to the next step. In the existing circumstances, there is a problem that several days are taken to salt loin ham or boneless ham, or to season roast pork.
Additionally, the injection pressure of brine for curing in the multi-needle pickle injector is limited to about 12 kg/cm.sup.2 owing to its structure. Among substances included in the seasoning liquid, a low-molecular substance such as salt can easily move inside the green meat. However, high-molecular substances, or substances having a high reactivity with meat constituent substances cannot easily move inside the green meat. As a result, the liquid is defectively dispersed.
For refinement in the existing multi-needle pickle injector, it is necessary to further increase the needle density of the multi-needle pickle injector. However, even a fine needle has a diameter of about 3 mm, and the width of a jig for fixing needles is also present. Therefore, it is difficult to improve the existing needle interval of 12-25 mm. Also, even if the improvement can be accomplished, the increase of the needle density is required, so that when the needles are put into and taken from the meat, resistance increases. Then, it becomes practically difficult to operate the device. Consequently, the injection by means of the multi-needle pickle injector cannot achieve an object of uniformly dispersing the liquid in the green meat in a short time.
Also, when the liquid is injected to a large green meat with the conventional multi-needle pickle injector, portions of one green meat have different hardnesses. Even if the liquid is tried to be uniformly injected, it cannot be uniformly injected because of a difference of injection resistance in meat property. For example, in Japanese Utility Model Publication No. 11799/1985 and Japanese Patent Application Laid-open No. 209693/1994, there are disclosed methods for solving the ununiformity of the brine for curing injection due to a difference between injection resistances of the meat. By the methods, however, it is difficult to obtain highly precise results. The methods are not satisfactory.
On the other hand, for the utilization of a needleless pickle injector and its injection method to a ham and another processed meat, the following prior art is known.
In Japanese Patent Application Laid-open No. 244906/1993, there is disclosed a method in which a liquid substance such as brine is introduced into a piece of meat with the needleless pickle injector under a high pressure by using spray nozzles. The pickle injector has a structure in which the thickness of a green meat is made constant by a pressure roller and a conveyor and the liquid substance is injected from the underside by the spray nozzles. Further, it is described that the interval between the nozzles is within 20 mm and the liquid substance can be injected into a 20 mm thick meat. Since diffusing spray nozzles are used in the pickle injector, as shown in FIG. 5 of the publication, the liquid substance spreads in a concentric manner. Non-injected portions and liquid overlapped portions are generated. It cannot be said that the liquid substance can be uniformly injected and dispersed by the method. Also, the pickle injector has a structure in which the meat is crushed and thinned, and the injection is then performed. The meat is damaged by a high spray pressure which concentrically spreads. Therefore, the pickle injector cannot be used for a thick meat.
Also in the method, the meat may be cracked and broken by the pressure roller.
Therefore, in the introduction method, even if thickness is reduced by the pressure roller, it is difficult to apply the method to pork ham or loin with a thickness exceeding 30 mm.
It is disclosed in the specification of U.S. Pat. No. 2,418,914 that, in order to soften meat in a short time after slaughtering, a meat softener of a lipid substance and a small amount of water or other edible particles are sprayed over a meat surface under high pressure at high speed and allowed to permeate through a depth of the meat and that meat muscle fibers are mechanically ruptured. However, the dispersed condition and the like of the edible particles are not detailed.
It is disclosed in the specifications of the U.S. Pat. Nos. 3,016,004 and 3,436,230 that a tip end of a nozzle is brought in contact with a meat surface to inject preservative liquid or another liquid under a high pressure and disperse the liquid without rupturing meat fibers. It is described as a concrete example that a high-speed liquid flow is injected to lean and fat of bacon belly by using an automatic injector which is provided with a lean injection nozzle and a fat injection nozzle.
In the specifications of U.S. Pat. Nos. 3,769,037 and 3,649,299, there is described a method for effectively limiting a penetration depth of liquid of softener and/or flavor application agent into meat. By allowing coherent stream from three directions to collide against one another at a focal point and losing and diffusing energy, the penetration depth is limited.
In a device described in the specification of the U.S. Pat. No. 3,675,567, while the injection nozzle described in the aforementioned specifications of the U.S. Pat. Nos. 3,769,037 and 3,649,299 is moved at the same speed as the meat, by the control of a solenoid valve which can be quickly turned on/off by an electric timer, softener, flavor application agent or another liquid is injected to poultry meat under a pressure of 1000 to 5000 psi and at a high speed.
The specifications of the U.S. Pat. Nos. 3,739,713 and 3,814,007 disclose an injection device in which liquid pressure in a nozzle path is increased until it reaches a predetermined value. After a valve is opened, liquid is quickly injected at a dash from tip ends of plural nozzle paths having various lengths in accordance with an amorphous green meat. In the device no liquid leakage occurs.
It is described in the specification of the U.S. Pat. No. 5,053,237 that to enhance softness and sensory quality of low-class meat, vegetable oil, fat or another binder is injected to a moving meat from a nozzle disposed at a predetermined distance from the meat under such a pressure that the binder can sufficiently penetrate through meat tissue. Meat connective tissue can be cut in transverse and vertical directions.
It is described in the specification of the U.S. Pat. No. 5,112,270 that, in order to perform water-jet slaughtering, cranium is ruptured under an ultra-high pressure (3000 to 4000 kg/cm.sup.2)
In the specification of U.S. Pat. No. 5,200,223, there is described a method in which liquid is intermittently or periodically jetted in the form of a fine jet flow in a short time from a high-pressure nozzle to meat continuously conveyed in a piping and the liquid is injected to a given depth of the meat.
In the specification of U.S. Pat. No. 5,176,071, there is described a method and a device in which, in order to improve a means for causing no damage on meat, a green meat on a conveyor is flattened to a predetermined thickness by a pressure roller and brought into contact with a spray nozzle. Without spraying injection stream to an outer surface of the meat, seasoning liquid or the like is uniformly dispersed.
However, in some of the aforementioned needleless pickle injectors and the injection methods using the injectors, the meat surface is damaged. In the other, the thickness of the green meat as an object is limited. They have no general-purpose properties. Above all, in a practical level for raw-material meat various in thickness, it cannot be absolutely said that the liquid substance can be uniformly dispersed. Then, an injection method in which the injection pressure is controlled while injecting the liquid substance in such a manner that the liquid substance can be uniformly dispersed and a pickle injector for use in the method have not been known.
On the other hand, a meat product is largely classified into a cooked meat product subjected to heating and sterilizing and a uncooked meat product not subjected to heating and sterilizing. A raw ham belongs to the uncooked meat product. By using salt or the like, its keeping quality is enhanced. As a curing method for manufacturing the raw ham, a dry curing method, a brine curing method and a single needle injection method are authorized according to the Japanese food hygiene law. Generally, in the dry curing method, after shaping raw-material meat, the meat is directly rubbed with salt or the like. After the meat is cured in a refrigerator for 2 to 3 weeks, decuring is performed as required. Thereafter, smoking/drying is performed for 3 to 7 days. In the brine curing method, after shaping raw-material meat, the meat is pickled in curing liquid of salt or the like dissolved in water for about 2 weeks. Decuring is performed as required. Thereafter, smoking/drying is performed for 3 to 7 days. In the single needle injection method of curing liquid, after shaping raw-material meat, curing liquid which is formed by dissolving salt or the like in water is injected with a needle. After the meat is cured in a refrigerator for 7 to 10 days, smoking/drying is performed for 3 to 7 days.
Among the aforementioned curing methods, in the dry curing method, the curing period is as long as 2 to 3 weeks as aforementioned. Much space in the refrigerator is necessary. The salt content of the product tends to be high. Additionally, there is a large difference of salt content in each product. In the brine curing method, the curing period is slightly shortened as compared with the dry curing method, but as long as about 2 weeks. Each product has a large difference of salt content in the same manner as in the dry curing method. According to the single needle injection method, it takes about 2 weeks to manufacture the raw ham. The method is superior in manufacture period to the dry and brine curing methods in which the manufacture period is three to four weeks. However, a predetermined quantity of the curing liquid needs to be manually injected uniformly to the green meat with one needle. Therefore, the method provides a bad productivity and requires skill in operation. It cannot be absolutely said that the method is efficient.
Also, for the raw ham, in a known method, to shorten the curing period, a pork block and Brine are thrown into a massage machine and massaging is performed to allow the Brine component to permeate the pork block. Thereafter, manufacture is performed in a conventional method. Thereby, manufactured is a raw ham which has a small salt-content gradient in its surface and central portion, a low salt-content concentration and softness (Japanese Patent Application Laid-open No. 149/1995). To obtain a raw ham with a little dispersion of salt concentration in a product, in a known method, raw-material pork salted in a high salt concentration is desalted by circulating brine with a salt concentration of 1 to 4% (Japanese Patent Application Laid-open No. 141763/1994). Also, to manufacture a raw ham, a raw bacon or another uncooked meat product in a short period, a block of livestock meat is scured by using a curing agent and 5 to 30 parts by weight of sugar relative to 100 parts by weight of the livestock green meat. Drying and smoking are performed in conventional methods. Such method of manufacturing a uncooked meat product is also known (Japanese Patent Application Laid-open No. 284877/1994).